Why I am only discovering this channel now! I have been using Darktable for a year or so but could not find good tutorials. This is great content and really helpful. Keep them coming!
Why don't all the Lens manufacturers just provide these Lens Infos for Lensfun (and others who need it). Should be in their interest. They could do that even before the lens is on the market. And thanks for the video. Did'd need the module so far but going through all of you videos (and ads for a tiny little support back) anyway so I've seen everything and know where to go and watch again if needed 😅
You're right. You would think the manufacturers would see the value in supplying that info. But maybe because lens fun is FOSS, there's no financial gain. Who knows?
I have a fish-eye lens (Pentax DA 10-17mm F3.5-4.5 ED). Often when I use it I want to embrace the distortion but other times I just use it for the wide field of view, in which case I use the "lens correction" module. In these cases the rectilinear geometry setting is often too extreme. It will get the lines straight but at the expense of losing a lot of the field of view, so I play with other geometry settings. I'll often end up with stereoscopic or sometimes panoramic but all settings are worth looking at.
Very useful as usual. I tried this on a couple of images that I took this morning and it made a tiny difference at the extremes of the lens, that I probably wouldn't have noticed. Probably worth it where there are important straight lines in the picture. Also, for a night sky panorama that I had issues with some time back. I think I might revisit that!! Thanks again!
Hi Bruce. Good to see you back on top form, and with so many new friends! There doesn't appear to be a performance hit when the module is active, so I tend to just turn it on by default, but rarely make any adjustments to the settings. To be honest I hadn't actually noticed the Distance box (which you left at 1000m for the boys on the beach!) so that's one to experiment with. I assume if your buildings are leaning, this would be a module to run before applying keystone corrections in crop and rotate. That's a video for your list - the best order to apply modules so they play nicely. It will be interesting to see the lens calibration procedures you perform to create the data, just to work out the physics going on. Fortunately I only have old Canon lenses, so they are in the database. :) Keep up the good work
Clear explanation as always , thanks for the great work. Now we are waiting for a video that explain all the steps needed to get your lens data in lensfun :)
Bruce - it would be great if you do a video to get your lens data into lensfun as it may encourage others, including myself, to submit their data and make the database more complete
It looks like the new Sigma 85mm DG DN has major distortion issue out of the box and they expect RAW editors to fix that on post processing. It's too bad DarkTable/LensFun don't support that :(
Outs not up to desirable to fix that, though. It's up to users to submit sample images with that lens to the lensfun database, so they can build a profile.
@@audio2u true that. It it were a cheaper lens, I might have gone through the route. I'm not going to spend $1300 on a lens a wait for a while to get the profile approved. We need a rich volunteer to do that :) in an Ideal world Sigma should have done this.
I use an extender w/my lens (Canon 1.4x). What's the impact of an extender on lens correction? I also noticed that the exif lens field value includes the extender in it (eg "Canon RF 100-400mm F5.6-8 IS USM + RF1.4x", which causes DT to not find the lens in the lensfun database xml file that dt includes. I can manually select the lens from the drop-down as you suggested as a workaround. I didn't see you mention how we should be updating the lensfun files as they continue to update them (I'm on Windows). Do we just pull down their XML files to the dt > lensfun > version_1 folder every so often?
I will confess to not being up to speed on how to update the lensfun database manually. As for the use of a teleconverter, I would imagine that that would completely destroy any usefulness of the lens correction module! It's effectively like adding a second lens to the equation. And I don't think it would be realistic for any database to hold every conceivable permutation of lens + teleconverter imaginable.... that would be orders of magnitude greater in terms of data. You would probably be best to do manual corrections by eye.
How you shoot and how you process your photos are two entirely different disciplines! I don't think anyone would say you 'shouldn't' be using an extender. If that's what you need to get your images, then so be it. I just don't think you can expect a lens correction algorithm to be able to compensate for every conceivable combination of extender and lens. :) And while I'm no expert in this field, I would suggest that lens correction at longer focal lengths is probably less of an issue than it is for shorter (wider) focal lengths.
Please , explain how to upload the profiles of our lenses? It would be very interesting as third party lenses, are hard to find, same as your Venus Laowa :) Thank you !!! Best from Uruguay. By the way, it seems that the person who created Lensfun is asking for managment of the program . I tried to understand what they explained and I couldn't LOL, marvelous old age, time to learn but sometimes it's too much! hahaha! :) :)
Bruce, thanks for reminding me that the lens correction mod is tied to LensFun and therefore that checking Lensfun for your particular lens is key. For example, I had forgotten that vignetting is not corrected for my 12mm Rokinon/Samyang (I plan to submit data) in the database. Also, how do you edit your exif data so that DT recognizes your lens when the camera does not, for example with manual lenses? I find exiftool to be very difficult to use.
Good question, Jack! Not something I've ever looked into. Probably because I don't keep records of what aperture I shot at with my manual focus lenses.
The same way you would apply ANYTHING in darktable to multiple images.... In the lightroom view, select one image which you have already applied those settings to, go to the Selected Images module, press 'selective copy', from the pop up list, deselect all, select the entry for the lens correction module, press copy, select the thumbnail for the first image you wish to copy those settings to, shift+select the last image you wish to copy those settings to, in the 'selected image' module, make sure the MODE is set to 'append' (not overwrite), then click paste.
I need to do some research. My Sigma 150-600 Contemporary lens is in the Sigma lens correction list but it is not automatically selected. I think the EXIF data string in the image doesn't match what lensfun checks against for the lens, it is always listed as (624). Cameras with same make lenses often correct many of these things when producing the JPEG and it can be very noticeable that it has not been corrected when viewing RAW especially on some of the newer compact/pocket cameras that let you now save RAW.
@@audio2u Yes. Recently someone in a local fb camera group was trying to get his head round RAW and was posting screenshots of RAW and out-of-camera JPEG in various applications and couldn't work out why the "shape" of the image in the screenshots varied so much. It was really noticeable in his compact at short focal lengths. The JPEGs "straightened" everything and as a result cropped out a lot of the image but working with the RAW file and trying to get parts of the cropped out image distortion free was very difficult.
@@audio2u I am no longer a member of the group so I can't check but it was a Canon of some kind because several of his comments were related to what Canon DPP software did before displaying an image when working with the RAW file i.e. applied the camera settings including lens correction, when other RAW software didn't.
I was wondering when to apply this module. I've read conflicting statement that it should be one of the last modules to apply, but I have always made it one of the first ones (after exposure) that I use. Does it matter where in the list of modules you use this?
The great thing about darktable is that it doesn't matter what order you ACTIVATE the modules in, because the pixelpipe has been designed to apply the modules in a predefined order regardless. If you click on the Active modules tab (left-most icon on the right hand side in the darkroom view), you'll see the exact order in which processing is being done, working from bottom to top.
@@audio2u but of course, as mentioned in my comment, if you apply keystone corrections and make it all nice, then you lens correct, the keystones could need redoing, so although it doesn't 'matter' it might be easier - no different to two modules that both change contrast or saturation of course. just a juggling act.
If I didn't mention it, my apologies. It's also possible that I didn't KNOW what it did, and therefore didn't say anything about it. When I'm in front of darktable, I'll try to remember to have a look and report back.
@@audio2u Ok, the preset is "correct" and the other option is "distort". I think and it looks like "correct" is, obviously, to correct the distortion, and "distort" is to distort even more the image, I don't see the point of doing such a thing though.
I use "Lens correction" pretty much every time I use darktable, I think it is a must to have the image as much optically correct as possible. But, opinions apart, I'm writing this comment because I had recently a weird issue with it that I can't explain, although it is not a serious one. I bought a Sigma 17-50mm F2.8 EX DC OS HSM (that is on the database) for my Canon EOS 70D, but it is identified as the Canon EF-S 17-55mm f/2.8 IS USM, it is not a big deal, I change it manually for the correct lens, but it is a bit annoying. Do you think is there any solution for this? Thanks in advance from Portugal and be safe.
That's an interesting one! I don't really know how the Lens Correction module does what it does, beyond "it reads the metadata embedded within the image".
@@audio2u just to be sure that it was darktable's problem I tried it on Rawtherapee, and it identified it correctlly. Thanks again by your answer, even you couldn't help me.
You use the configuration file exiv2.ini (Windows) or .exiv2 (Linux). Open the text document and pair the LensType nr, that is 240 for 17-55, with your lens. 240=Sigma 17-50mm f/2.8 EX DC OS HSM
Very helpful tutorial as always :). It would be great if it was possible to use a lcp file from Adobe. You can do that in Rawtherapee. So if for an example your lens is not included in the lensfun database, you can see if your lens exist as a lcp file. Which it usually does.
This is possible using the 'lensfun-convert-lcp' command. This is a Python script located in '/usr/bin/' in Linux. I have no idea if it gets installed in Windows. These converted lcp-files are placed as lensfun XML-files in '/home/user/.local/share/lensfun' (Linux) and automatically recognized by darktable. More info at wilson.bronger.org/lensfun/lensfun-convert-lcp.html Using this command I converted the Adobe lcp profile for the 'Venus Laowa 15mm F2 Zero-D': Venus Laowa 15mm f/2 Zero-D Sony E 1.0 When converting the lcp profile from the Venuslens website I get the following lensfun profile: Venus Laowa FE 15mmf/2 D-Dreamer (JPEGs) Sony E 1.0
@@bertblockx7102 Thank you :). I tried that but darktable couldn't find the xml. I tried to remove acm from xml and now darktable could find xml, but then the image got very distorted. Maybe I did something wrong. I will try again later. But thank you so much :). An update: Now it works :). I compiled latest lensfun (0.3.95) and also compiled darktable. After that run lensfun-convert-lcp. So now it's possible to have lenses that is not official supported by lensfun :). The problem before was that the darktable used an older version of lensfun, which doesn't support Adobe lcp database v2. And v2 is required for acm support.
Hi Bruce. Been following your tutorials for some time now and it was all going swimmingly. Easy to follow instructions from you has made life easier. Been through many of the videos more than once, HOWEVER - I upgraded from the Canon 80D to the 90D and just found the Darktable doesn't support CR3 files. As you are the "font of all knowledge" on this software, do you know if and when Canon will allow the information to be available to Darktable team to make the changes??
I am FAR from the font of all knowledge! Bwahaha! I know there's a major (and out-of-cycle) darktable release coming in August, so hopefully there will be CR3 support then.
Nice video Bruce...do you think the aperture setting can have a significant effect....when you went to f8...it looked like your image got substantially brighter....??
I guess that comes down to the quality of the profile for that lens. And that is probably determined by the number of images submitted to Lensfun. If multiple images, covering all apertures, were submitted, maybe that helps? Just a guess.
Replaying the section and watching different parts of the image shows it lightens the edges. Vignetting can be more noticeable at larger apertures so setting the aperture used for the shot will "correct" the image the right amount. Correcting the vignette can be important if your applied crop is not symmetrical, you might have dark left corner but no darkening of the right corner - so correct the vignette then perhaps apply your own if that is what you want.
darktable uses a third party database called lensfun. I believe you can go to the lensfun website and they have instructions on how to create test images with your lens so that you can then submit that lens to the database. If you don't feel like doing that, then it's just a case of waiting for someone else to do it. Oh course, it's possible that the website has an updated version which does include you're lens. In that case, you would need to manually update your version of lensfun, but I don't know how to guide you on that, sorry.
Thanks Bruce! If there is no lens information available from the exif, is the available lens list filtered by the lens mount of the camera so only lenses are displayed that make sense? Or is every lens from the database available independent of the camera? Keep up your great work!
I'm guessing (don't know for sure) that the lens list in the LC module IS filtered to the mount. Otherwise, you'd be looking at hundreds of lenses all the time!
